Tag Archives: Filter

• Beach Huts •Using polarising filters reduce glare, reflection and colour fade in your photograph. These filters are easy to use and produce great results. [Image from the video]

Filter with a hidden impact

Photographic filters are light modifiers. They have a variety of different effects. Polarising filters are just one type of photographic filter. When you look at one it appears dark. It looks as if it would have no effect except to reduce the light in your image.

What does using polarising filters do for your photo? Light from the sun tends to be scattered by the atmosphere. The waves of light are out of alignment. When the light is very bright the glare causes a bright haze of light. This over-brightness can act to overwhelm a photograph. It especially tends to wash the colour out of the sky, whitening it. Using polarising filters helps reduce the glare. It filters out some of the light that is not aligned. Only the polarised light passes through the filter. This aligned light has reduced glare allowing the colours to come out. Skies are darkened. Reflections are reduced.

The results of using polarising filters

• Worst and best case scenario for using polarised filters • Careful positioning and using polarising filters dramatically affects the outcome.

Using polarising filters can have a dramatic effects on your image. The top picture shows the worst case scenario. Light is almost directly into the lens. It is bouncing off glass and polished surfaces into the lens too. The sky is very bright with scattered light from direct, harsh sunlight. There is a hazy glare from brightness. There is also flare and very bright spots from reflections. This photo was taken without using a polarising filter.

In the second (lower) photo the position is different. The direct sunlight is not directly entering the lens. Even so, without using a polarising filter there would be problems. Notice the bright blue sky. This would have been a very washed-out blue on this very sunny day. Notice the windscreen is almost transparent? The polarising filter has reduced the bright reflections and specular highlights. The reflections on the bonnet are also pleasant and not over-white. The car paintwork has a quality colour-depth. The whole quality of the lower photo seems better. All this despite the harsh direct light.

Actually using polarising filters

In the video Mike Browne shows how to use these useful filters. In particular you need to remember three things of particular interest…

Using polarising filters is most effective when the light is coming at the lens from about 45° off the optical axis.

While using polarising filters you will need to rotate the filter to find the most effective polarising position. You need to re-adjust it every shot. Each shot will have a different angle of light to the lens.

Using polarising filters reduces the light able to enter the lens. Your light may be reduced by over two stops with a poor quality version.

Quality

High quality Polarisers are more expensive. They are time consuming and expensive to make. They also use expensive materials. However, the better ones maintain photographic quality. So it is worth spending the extra money. Poor quality polorisers may increase the digital noise from light scatter in the filter. They may also create aberrations and distort the image.

All photographic filters reduce the light entering the lens. A quality polariser will also reduce the light. But, they will affect the light much less than a poor quality polariser. Using polarising filters of a low quality may reduce the incoming light by as much as three stops. A quality polariser will tend to reduce light by only two stops (or less). So think carefully about what you purchase.

Buy now…

When buying a circular polarising filter make sure you get one that is the right size. The filter size of your lens is normally written on the inside of the front of the lens.

Recommended!

When using polarising filters buy the size that fits your lens. Also remember that the quality of the filter can affect the photo. High quality polarisers reduce aberrations. A higher quality filter will not reduce the light as much as a poor quality one.

Damon is a writer-photographer and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photogs.See also: Editors ‘Bio’. By Damon Guy see his profile on Google+.

Damon is managing editor of Photokonnexion.com with professional experience in photography, writing, image libraries, and computing. He is also an experienced, webmaster and a trained teacher. Damon runs regular training for digital photographers who are just starting out.See also: Editors ‘Bio’By Damon Guy :: Profile on Google+

Getting the sky right is important.

With the holiday season approaching we want our holiday photographs reflect the happy memories. All too often the sky is over-white, washed out or blown-out. There are a number of techniques you can use to get the sky right, in camera and in post processing.

What are you really looking for in a good sky? Deep blues for the sky, fluffy white clouds and well defined horizons are the ideal situation. To get them like that in the camera you have to pay attention to the time of day, the type of sky, the weather and have a sense of drama. Here are some ideas to help you…

Polarizing Filter

One of the photographers important tools for sky photography is the polarizing filter. It is a glass or composite material that is set into the inner of two metal rings. The first ring screws directly to the front of your lens. The other rotates inside the screw ring. The filter itself cuts out some of the wavelengths of light. You turn the ring with the filter mounted in it so that it can be set for maximum effect. The filter action reduces the glare and haze associated with reflective surfaces like water and glass. Amazingly it also deepens the blue in the sky. So what we see in the photograph is a sky that is darkened with emphasised blues and the air has a crispness and clarity. These effects are not reproducible in post-processing software. It is invaluable to have this effect in camera and will really liven up the drama of the sky.

Critical view-line

If you gaze out across a wide open sky on a bright sunny day you will notice that the blueness of the sky is not uniform. It is a deeper blue in places and a whiter blue elsewhere. In fact the sky gets to be a deeper blue if you are facing away from the sun. It is at its deepest blue at the opposite end of the sky from the sun. So where you can, shoot with the sun at your back.

Of course having the sun at your back is not always possible. A good rule is not to let the sun be in front of you. If it is at your shoulder (90 degrees to your shot) it will still allow you to get a reasonable blueness in the sky. If you have to shoot with the sun in front of you, even if at a wide angle, the blues will start to whiten. The more you are shooting toward the sun the more the sky will wash out.

The mid-day washout

During the middle of a sunny day the sky will be at its most washed out. As the sun is at its highest at this point you should avoid taking photographs if you can. The more the sun falls toward the horizon the more the atmosphere will act as a natural filter and increase the blues at the opposite end of sky. The middle of the day is also bad for photography because the sun being overhead means that objects on the ground have little shadow around them. This gives the landscape a flat and unappealing look. Washed out skies and flat appearance at ground level makes convincing photography difficult!

Use an ND graduated filter

Neutral density filters are great. They are fun to use and give you back some of the blueness in the sky caused by over brightness. They don’t enhance the blueness like the polarized lenses. They are a way of cutting the light down so its intensity is reduced.

Without an ND filter the sky will tend to be over-bright, or the ground will tend to be too dark on a bright day. The graduated ND is an ideal tool for helping to balance the light levels. A full ND filter will reduce the incoming light right across the lens. However, a graduated ND filter allows the full amount of light to enter the lens from the lower half – which keeps the foreground bright. On the upper half of the filter (pointing at the sky) the neutral grey graduates from the very light across the middle to its darkest at the top of the filter. You place the beginning of the neutral grey on the horizon and then the grey graduates darker up the filter so the most washed out or over-exposed parts of the sky at the top of the picture are the parts with the most reduced light levels.

It is worth remembering that you can use both an ND graduated filter and a polarizing filter. However, also remember that each time you put a glass element in the line of light you will be reducing the light that can get into the camera. So remember to adjust your exposure to compensate for the additional glass.

The use of ND filters helps to bring out the clouds too. Brightness in clouds can be pretty harsh, especially if they are very dense. This tends to make them featureless. The use of ND filters for clouds (an ND 2 or 4 – the lowest filter levels) will help to reduce the brightness and enhance the contrasts in the darker parts of the cloud. This brings out its features and helps the cloud to take on a little depth.

Post processing sky enhancements

In post processing you can do a number of things to enhance your sky. However, after years of working on my skies I know that you can get better results in camera… try that first.

On trick to enhancing a washed-out blue sky is to use a saturate tool. Simply wipe the tool across the blue of the sky to deepen and lift the crispness of it. The saturate tool in most image editing applications tends to turn sky blue to turquoise blue. Don’t use full saturation. Set your saturation tool to between 10% and 20% and wipe it several times rather than one heavy wipe. With most tools/brushes it is better to use low exposure/opacity rather than be heavy handed. Not only is it more controllable but you can also build up to a reasonable blueness without over-doing it.

You should watch out that you do not wipe the saturate tool over the clouds. You will find that the clouds look white, but contain a high blue component. If you saturate them they turn blue to the eye – which looks highly unrealistic.

The trick to increasing the contrast in clouds is not the saturate tool. It is to deepen the grey of the darker parts of clouds using the burn tool. The burn tool darkens a colour by increasing its black component. Again, with the burn tool use a reduced exposure. I like to work with about 15% in clouds. Set the tool to mid-tones so the grey parts of the cloud don’t turn black. The idea is to increase the contrast not to give the clouds harsh deep lines – that would hardly match with the surrounding blue sky.

Blue sky thinking

If you really want to get the best skies then work later or earlier in the day to get lower wash-out levels in the sky. Make sure that where you can shoot away from the sun = especially toward the horizon with the sun at your back. Where brightness levels are high and you have to shoot you can reduce the wash-out with polarization and ND grad. filters. You can also post process the skies after your shoot, but this is not as easy as it sounds.

True blue-sky thinking is done before you take the shot. Deploy all the suggestions above and your skies will be blue. Have a happy holiday.

By Damon Guy (author and Photokonnexion editor)

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photographers.See also: Editors ‘Bio’.

Buy the right screw-on filter.

If you get it wrong it will not fit your lens. Not all of them are the same. You need to know with certainty you have the right one.

The importance of size

Lenses have different diameters. The end of the lens, where the filter screws onto the lens thread, is also of a different diameter. So here is how you know what size lens you want. If you look at the picture above you can see the lens is marked on the frame at the side. That mark is the filter thread size mark. It is accompanied by the filter size in millimetres. That is the size you need to quote to the dealer when you are asking for the filter size.

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Sometimes the size is found on the side of the lens, but it is normally accompanied by the size mark… ” Φ “ . Some lenses don’t have the mark and size of the filter. In this case the lens manual/leaflet will provide the size for your lens. In the case where you no longer have a lens manual/leaflet you should be able to look the lens specification up on the lens manufacturers website.

Filter adapters

Filters can be very expensive to buy. If you have several different lens sizes it is cheaper to buy a lens adapter for your lenses to fit the filter. So look at the filter manufacturers website to get the details on the filter adapter sizes.

The sky is no limit

One of the great problems of photography is contrast. A very bright sky loses its colour as it tends to over expose – trending toward white. Meanwhile the ground is well exposed. Here we look at one way to bring back that colour.

Polarizing Filters

If you read Skylight and UV filters you will know that the use of filters to cut out ultraviolet light is largely unnecessary with digital cameras. Polarizing filters on the other hand deal with the visible light we see in daylight. These filters have two purposes.

First, they have the effect of darkening the sky. This helps to off-set the over-exposure effect of brightness. It brings back the blue colour. This adds saturation to the sky’s own colour.

The other effect is on reflections. The polarizing filter helps to reduce reflections from some surfaces. This is often used to reduce excessive effects of sunlight on glass, or the intense reflections from water surfaces. The result allows us to see through the glass or into water.

In the video the presenter examines the effects of polarizing filters and how to use them. One of the types he shows is the circular filter, probably the most common type in use today. Watch carefully at how he adjusts it. This is an important technique. If you just mount the filter and don’t adjust it the effect can be too strong. This is a common mistake with less experienced users.

• UV and skylight filters • There is a debate about how useful they are…

What are UV and Skylight filters?

The keen starter in photography wants to protect their investment… Filters protect your lens – right? Or, is it that they stop damage from the sun? I want to clear up some myths and explain some half truths in this article. You may also save some money.

What are these filters for

Skylight and UV (UltraViolet) filters have a single purpose… to reduce ultraviolet light reaching film. The only difference between them is that skylight filters have a slight pink colour. Both filters prevent the slight tendency of some chemical films to acquire a slightly blue colour cast under some light conditions. (Yes, we are talking about film).

That was simple, wasn’t it?

Now the myths cleared up

UV and skylight filters have a number of myths surrounding them.

They prevent sunlight damaging my digital image sensor.
• No, they don’t. Sensors are UV insensitive or have built in filters (for both infra red and ultraviolet). UV (and IR) light has no effect on them.

They prevent the blue colour cast on sunny days.
• Not true. It is about 25 years since ultraviolet sensitive film was on sale. Even then, the film brands that were sensitive tended to only be sensitive in relatively few conditions; eg. when it was sunny at high elevations or beside the sea.

They provide more clarity in bright sunlight or at high elevations (over say, five thousand feet).
• Once upon a time… some colour film brands used a chemical that was sensitive to UV light. Around 30 years ago an ultraviolet inhibitor was developed that reduced the sensitivity of the film. Problem solved. The slight lack of clarity caused by the sensitivity went away.

They prevent lighter greys being over-bright when in black and white mode.
• Silver-based chemical black and white films were affected by UV. This is not a problem in digital cameras.

The skylight filter has slight pinkness that warms the picture up.
• No it doesn’t – pink is not a warming filter colour. Pink reduces blues in the image. Anyway, if you use auto-white balance any colour effect will be wiped out. If you use RAW there is no need for a filter as you can adjust in developing.

Actually these filters have problems

It turns out that UV and skylight filters can cause a few problems. Poor quality filters; inappropriate filter materials and lack of special coatings all take their toll…

Image effects…
Affects are created by using these filters. In particular over-exposure haze, flare and ghosting are created. The haze results from light bouncing between filter, lens elements and the sensor inside the body of the lens/camera. This creates a slight haze of over-exposure in very bright conditions. Flare, and therefore reduced contrast in the image, is sometimes caused by a beam of bright light being scattered by the filter. More expensive filters reduce this by having chemical coatings on (lens glass has coatings too). Ghosting is where spots of light appear in the image that were not in the scene. They originate from back reflection off the sensor onto the other lens elements or the filter. Usually this happens in low light situations stimulated by bright lights like car headlights.

Adding another glass (or resin/plastic) element…
Additional elements degrade the image. Cheaper filters can cause chromatic aerations, creating colour banding in an image. There may be additional light scattering. Some filters significantly reduce the light getting through (maybe as much as 1/3rd of a stop of light) leading to underexposure. Optical aberrations may be caused by poor alignment of the filter element (not flat/parallel) in its place. This causes loss of definition, particularly in some places where sharpness would be expected.

Are there any reasons to buy them?

Yes, but not many.

Protection:
UV and skylight filters do provide protection, creating a barrier against mechanical damage to your lens. The front elements glass or coatings on the surface are protected from dust, dirt, splashes and possible scratches or breakage from a bump, scrape or blow.
• Alternatively, consider a proper lens hood. They prevent angular light beams straying into the lens which can improve the image. They also greatly reduce the probability of damage to the lens too. Lens hoods are cheaper than filters, and don’t cause optical problems.

Supporting your dealer:
Filters are expensive to buy, but are profitable to sell. In these hard economic times you will be providing a rich return for your dealer and helping him survive a tough market.

A mistake to clear up

Somebody told me recently, “I always have this polarising filter on the front of my lens”. Wow! (It was actually a skylight filter when I looked). Polarising filters are great for reducing some reflections from some surfaces and may darken skies in some light conditions. Some people mix them up with UV and skylight filters. Just let me say for now, don’t keep a polarising filter on your camera.

By Damon Guy (author and Photokonnexion editor)

Damon Guy (Netkonnexion)

Damon is a writer-photog and editor of this site. He has run some major websites, a computing department and a digital image library. He started out as a trained teacher and now runs training for digital photographers.See also: Editors ‘Bio’.